Portable device capable of controlling output characteristics of adaptor, and corresponding method

ABSTRACT

A portable device capable of controlling output characteristics of an adaptor used for charging a battery of the portable device includes a sensing circuit and a controlling circuit. The sensing circuit senses a condition of the battery. The controlling circuit controls the adaptor to adjust its output characteristics based on the condition of the battery.

TECHNICAL FIELD

The present invention relates to a charging scheme for controlling anadaptor, and more particularly to a portable device capable ofcontrolling output characteristics of the adaptor and correspondingmethod.

BACKGROUND

Generally speaking, when a conventional adaptor is connected to anelectronic device via a communication interface to charge a battery ofthe electronic device, the conventional adaptor usually employs aconstant current to charge the battery in a constant current mode.However, under some conditions, considering the circuit costs and worsepower dissipation, only a smaller constant current can be employed forcharging the battery. The smaller current indicates that it is necessaryfor the conventional adaptor to consume a longer time period to chargethe battery. This drawback is unacceptable by users. Accordingly, it isimportant to provide a novel charging scheme to overcome the shortcomingof the prior art.

SUMMARY

Therefore one of the objectives of the present invention is to provide aportable device and method capable of controlling output characteristicsof an adaptor used for charging a battery of the portable device, tosolve the above-mentioned problems.

According to an embodiment of the present invention, a portable devicecapable of controlling output characteristics of an adaptor used forcharging a battery of the portable device is disclosed. The portabledevice comprises a sensing circuit and a controlling circuit. Thesensing circuit senses a condition of the battery. The controllingcircuit controls the adaptor to adjust its output characteristics basedon the condition of the battery.

According to an embodiment of the present invention, a method foremploying a portable device to control output characteristics of anadaptor which is used for charging a battery of the portable devicecomprises: sensing a condition of the battery; and controlling theadaptor to adjust its output characteristics based on the condition ofthe battery.

According to an embodiment of the present invention, an adaptor used forcharging a battery of a portable device is disclosed. An outputcharacteristic of the adaptor is configurable according to a conditionof the battery.

According to the embodiments, the portable device can communicate withthe controllable adaptor via a variety of communication interfaces andcontrol output characteristics of the controllable adaptor, to achievethe purpose of fast charging, avoid thermal damage, enhance/improve thewhole charging efficiency, and to save more power.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram of a charging system according to an embodiment ofthe present invention.

FIG. 2 is a diagram illustrating a safe operating area of the conductivecircuit element as shown in FIG. 1.

FIG. 3 is a diagram illustrating I-V curve of the adaptor according tothe embodiments of FIG. 1.

FIG. 4 is a control flowchart of the operations of the charging systemas shown in FIG. 1 according to an embodiment of fast charging in thepresent invention.

DETAILED DESCRIPTION

Please refer to FIG. 1, which is a diagram of a charging system 100according to an embodiment of the present invention. The charging system100 comprises an adaptor 105 such as an AC-to-DC traveler adaptor (butnot limited) and a portable device 110 such as a mobile device (e.g. asmart phone device, a tablet). The portable device 110 comprises aconductive circuit element 1101, a resistor 1102, a battery 1103, asensing circuit 1104, and a controlling circuit 1105. The sensingcircuit 1104 and the controlling circuit 1105 can be regarded as abattery charger device which can be implemented by using an integratedcircuit chip. The adaptor 105 is used for converting an AC source intoDC charging voltage Vchg and charging current Ichr and providing thecharging voltage Vchg and charging current Ichr for charging the battery1103 of portable device 110. In addition, the adaptor 105 is capable ofproviding a variety of different charging voltages and charging currentsfor the battery 1103 based on different conditions of the battery 1103.The output characteristic of the adaptor 105 is configurable accordingto a condition of the battery 1103. The portable device 110 can informthe adaptor 105 of the condition of the battery 1103 such as a batteryvoltage, and control the adaptor 105 to dynamically output differentcharging voltages and charging currents under different conditions.Preferably, this can achieve rapidly charging the battery 1103 of theportable device 110 and avoid that power dissipation exceeds a powerdissipation threshold. The conductive circuit element 1101 in thisembodiment is implemented with (but not limited) a bipolar junctiontransistor or a MOS transistor. The battery 1103 includes at least onecell. The sensing circuit 1104 is coupled to the battery 1103 and usedfor sensing a condition of the battery 1103. For example, the sensingcircuit 1104 senses the battery voltage Vbat of the battery 1103 togenerate a sensing result of the battery voltage Vbat. The controllingcircuit 1105 is coupled to the sensing circuit 1104 and used forcontrolling the adaptor 105 to adjust its out characteristics based onthe condition of the battery 1103. The controlling circuit 1105 candetermine the desired charging voltage and/or charging current that aresupplied from the adaptor 105 based on the sensing result of batteryvoltage Vbat. The controlling circuit 1105 informs the adaptor 105 ofthe determined charging voltage and charging current by sending controlsignals to the adaptor 105 via a specific communication interface suchas via the VBUS line of USB communication interface, via a dedicatedcommunication line of USB communication interface, or via anycommunication interface between the adaptor 105 and the portable device110. The adaptor 105 can provide the charging voltage and chargingcurrent determined by the portable device 110 for charging the battery1103 according to the control signals. Specifically, in order to achievefast charging and thermal protection simultaneously, the portable device110 controls the adaptor 105 to supply a maximum charging current to thebattery 1103 as far as possible. The maximum charging current that canbe provided by the adaptor 105 depends on a condition of the battery1103 and a power dissipation threshold associated with the thermalprotection. In this embodiment, the condition indicates the batteryvoltage Vbat, and the power dissipation threshold Pdmax of theconductive circuit element is considered as the power dissipationthreshold associated with the thermal protection. However, this is notintended to be a limitation. In other embodiments, the power dissipationthreshold associated with the thermal protection may be a threshold ofanother different circuit element included within the portable device110. In order to achieve fast charging and avoid the power dissipationof the conductive circuit element 1101 exceed above a power dissipationthreshold Pdmax, the controlling circuit 1105 controls the adaptor 105to adjust and then provide the charging voltage Vchg after determiningthe maximum charging current that can be provided by the adaptor 105 asfar as possible so that the provided charging current and chargingvoltage would not result in a power dissipation exceeding above thepower dissipation threshold Pdmax. The relation of power dissipationresulted from the conductive circuit element 1103 can be calculatedaccording to the following equation:

Pd=(Vchg−Vbat)×Ichr

wherein Pd indicates the power dissipation, Vchg indicates the outputcharging voltage outputted by the adaptor 105 for charging the battery1103, Vbat indicates the battery voltage, and Ichr indicates thecharging current. The battery voltage Vbat can be sensed by the sensingcircuit 1104, and accordingly the controlling circuit 1105 can adjustthe charging current Ichr and output charging voltage Vchg in order tomaximize the charging current Ichr and avoid the power dissipation Pdexceed the power dissipation threshold Pdmax. That is, in order toincrease the charging current Ichr as far as possible, the portabledevice 110 is arranged to decrease the voltage difference between theoutput charging voltage Vchg and the battery voltage Vbat. Thus, bymaximizing the charging current Ichr that can be supplied from theadaptor 105, the battery 1103 can be charged rapidly, and thissignificantly reduces the whole charging time. In this situation, thecontrolling circuit 1105 may set the output charging voltage Vchg as avoltage level that is lower than a level calculated based on themaximized charging current Ichr, so that the corresponding powerdissipation Pd is slightly smaller than the power dissipation thresholdPdmax and the conductive circuit element 1101 is not damaged. That is,after determining and configuring the charging current Ichr provided bythe adaptor 105, the portable device 110 can control the adaptor 105 toselectively output or supply different output charging voltage levels.For example, a first level may be determined based on theabove-mentioned equation and the maximized charging current, and asecond level may be a level which is slightly lower than the firstlevel. The selection of supplying different output charging voltagelevels according to the same charging current provides a flexibility ofoutputting different powers. The portable device 110 controls theadaptor 105 to select one of multiple charging levels corresponding todifferent powers and provide the selected voltage for the battery 1103under different conditions.

As mentioned above, the portable device 110 (or the controlling circuit1105) can be used for configuring the charging current Ichr supplied bythe adaptor 105 based on the battery voltage Vbat, determining theoutput charging voltage Vchg provided by the adaptor 105 according tothe configured charging current Ichr, and controlling the adaptor 105 tooutput the determined output charging voltage Vchg and the configuredcharging current Ichr. Accordingly, the portable device 110 includingthe sensing circuit 1104 and controlling circuit 1105 is capable ofcontrolling output characteristics of the adaptor 105. The outputcharacteristics may indicate (but not limited to) the charging currentIchr or the output charging voltage Vchg. In other examples, the outputcharacteristics may include AC-to-DC switching frequency, AC-to-DC biascurrent, the precision of output voltage, voltage ripple, and thedynamic loading, etc. The portable device 110 can also be used tocontrol the output characteristics of the adaptor 105 by adjusting atleast one characteristic of AC-to-DC switching frequency, AC-to-DC biascurrent, the precision of output voltage, voltage ripple, and thedynamic loading, etc., so as to adjust the charging current Ichr.

It should be noted that the controlling circuit 1105 can adjust theoutput charging voltage Vchg after determining/configuring the chargingcurrent Ichr in a first embodiment or can adjust the charging currentIchr after determining/configuring the output charging voltage Vchg in asecond embodiment according to the equation of power dissipation ofconductive circuit element 1101.

In the embodiments, the conductive circuit element 1101 can beimplemented with a bipolar junction transistor. The bipolar junctiontransistor is turned on and becomes saturated when the adaptor 105 ischarging the battery 1103. The voltage drop between the collector andemitter of the bipolar junction transistor is marked as VCE which insome examples may be equivalent to 0.25 Volts-0.4 Volts. The voltagedifferent between the output charging voltage Vchg and battery voltageVbat can be represented by VCE+Ichr*R wherein R indicates the resistancevalue of the resistor 1102 disposed between the bipolar junctiontransistor and the battery 1103. The resistance value is very small andcan be ignored. The voltage different between the output voltage Vchgand battery voltage Vbat is almost equivalent to VCE. Accordingly, themaximum of charging current Ichr can be calculated or estimated by thefollowing equation:

${I\; \max} = \frac{{Pd}\; \max}{V_{CE}}$

Imax indicates the maximum of charging current Ichr. For example, if thepower dissipation threshold Pdmax is designed as 0.7 W, then the maximumcharging current Imax can be configured as 2.8 A−1.75 A that isdependent upon the voltage drop VCE between the collector and emitter ofthe bipolar junction transistor. If the voltage drop VCE is equal to0.25 Volts, the maximum charging current Imax can be configured as 2.8A. If the voltage drop VCE is equal to 0.4 Volts, the maximum chargingcurrent Imax can be configured as 1.75 A. The controlling circuit 1105of portable device 110 is arranged to control the adaptor 105 to outputthe maximum charging current Imax as the charging current Ichr for thebattery 1103 and output the output charging voltage Vchg that is equalto the sum of the voltage drop VCE and battery voltage Vbat. The outputcharging voltage Vchg supplied by the adaptor 105 can be dynamicallyadjusted according to the change of the battery voltage Vbat since thebattery voltage Vbat can be sensed by the sensing circuit 1104 and thevoltage drop VCE can be determined. That is, the portable device 110 cancontrol the adaptor 105 to output the stable maximum current Imax anddifferent charging voltage levels based on the different levels of thebattery voltage Vbat. Thus, the battery 1103 can be rapidly charged withthe maximum charging current Imax in a constant current mode.

Please refer to FIG. 2, which is a diagram illustrating a safe operatingarea of the conductive circuit element 1101 such as the bipolar junctiontransistor as shown in FIG. 1. As shown in FIG. 2, in addition toconfiguring the charging current Ichr as the maximum charging currentImax, the controlling circuit 1105 can also configure the chargingcurrent Ichr as any currents that are smaller than the maximum chargingcurrent Imax, and can control the adaptor 105 to adjust the outputcharging voltage Vchg or not to adjust the output charging voltage Vchg.The dotted line area of FIG. 2 indicates that the conductive circuitelement 1101 is not damaged due to thermal damage caused by the powerdissipation when the conductive circuit element 1101 is turned on andbecomes saturated. That is, the dotted line area represents the safeoperating area of the conductive circuit element 1101. For example, thecharging current Ichr may be configured by the portable device 110 as acurrent (e.g. 368 mA, 500 mA, or 777 mA) that is smaller than themaximum current Imax such as 1.75 A. The portable device 110 (orcontrolling circuit 1105) correspondingly. sets the output chargingvoltage Vchg as 5.5 Volts, 5 Volts, or 4.5 Volts when the level ofbattery voltage Vbat is equal to 3.6 Volts. The combination of 500 mAand 5 Volts (or the other combinations of voltages and currents)indicates that the adaptor 105 can output more or maximum power. Inaddition, when the portable device 110 configures the charging currentIchr as a current smaller than the maximum current Imax, the portabledevice 110 can control the adaptor 105 to output different voltagelevels for charging. For example, when the portable device 110configures the charging current Ichr as a current of 777 mA smaller than1.75 A, the portable device 110 can control the adaptor 105 to outputdifferent voltage levels 4 Volts-4.5 Volts for charging. Similarly, whenthe portable device 110 configures the charging current Ichr as acurrent of 500 mA, the portable device 110 can control the adaptor 105to output different voltage levels 4 Volts-5 Volts for charging. Thecharging current Ichr becomes smaller, and the range of output chargingvoltage level becomes wider. It should be noted that the example shownin FIG. 2 is merely used for illustrative purposes and is not intendedto be a limitation of the present invention; in other examples, thebattery voltage Vbat may be changed with time when the adaptor 105continuously charges the battery 1103, and the safe operating area ofthe conductive circuit element 1101 becomes different correspondingly.In addition, the maximum power dissipation (i.e. power dissipationthreshold) of the conductive circuit element, 0.7 W, is merely used forillustrative purposes and is not intended to be a limitation of thepresent invention.

Please refer to FIG. 3, which is a diagram illustrating I-V curve of theadaptor 105 according to the embodiments of FIG. 1. The controllingcircuit 1105 is arranged to adjust the charging current Ichr afterdetermining/configuring the output charging voltage Vchg. As shown inFIG. 3, for example, the controlling circuit 1105 or the portable device110 can control the adaptor 105 to supply a current of 1 A (i.e. thecharging current Ichr) and 5 Volts (i.e. the output charging voltageVchg) for charging the battery 1103. The adaptor 105 is capable ofproviding the power of 5 W. Alternatively, the controlling circuit 1105or portable device 110 can control the adaptor 105 to decrease andconfigure the output charging voltage Vchg as 4.6 Volts that is lowerthan 5 Volts, and then control the adaptor 105 to select one currentvalue from a range of 1000 mA-1086 mA as the charging current Ichr forcharging the battery 1103. If the charging current Ichr is configured as1086 mA, then this indicates that the adaptor 105 is still providing theoutput power of 5 W almost. The adaptor 105 substantially keeps itsoutput power at 5 W. Also, the charging current Ichr can be stillconfigured as 1 A. Alternatively, the controlling circuit 1105 orportable device 110 can control the adaptor 105 to decease and configurethe output charging voltage Vchg as 3.8 Volts lower than 4.6 Volts, andthen control the adaptor 105 to select one current value from a range of1000 mA-1315 mA as the charging current Ichr for charging the battery1103. If the charging current Ichr is configured as 1315 mA, then thisindicates that the adaptor 105 is still providing the output power of 5W almost. The adaptor 105 substantially keeps its output power at 5 W.Also, the charging current Ichr can be still configured as 1 A or 1.086A. That is, when the controlling circuit 1105 (or portable device 110)configures the charging voltage Vchg as a lower level, the chargingcurrent Ichr that can be supplied by the adaptor 105 to the battery 1103can be increased for rapidly charging the battery 1103 especially in aconstant current charging mode, and the adaptor 105 is capable ofsubstantially keeping its output power at a rated maximum output powersuch as 5 W.

In order to make readers easily understand the spirit of the presentinvention, FIG. 4 is provided to show a control flowchart of theoperations of the charging system 100 as shown in FIG. 1 according to anembodiment of fast charging in the present invention. Provided thatsubstantially the same result is achieved, the steps of the flowchartshown in FIG. 4 need not be in the exact order shown and need not becontiguous, that is, other steps can be intermediate. The steps aredetailed in the following:

Step 405: The controlling circuit 1105 of portable device 110 (i.e. acharging host) communicates with the adaptor 105 via a specificcommunication interface such as a USB communication interface;

Step 410: The controlling circuit 1105 of portable device 110 checkswhether the adaptor 105 is a controllable adaptor or not. If the adaptor105 is controllable, the flow proceeds to Step 415, otherwise, the flowproceeds to Step 450;

Step 415: The controlling circuit 1105 of portable device 110 determinesor calculates the maximum charging current Imax according to the powerdissipation threshold Pdmax and the voltage drop VCE across theconductive circuit element 1101, and configures the charging currentIchr as the maximum charging current Imax;

Step 420: The sensing circuit 1104 senses the battery voltage Vbat, andthe controlling circuit 1105 gradually raise up the charging voltageVchg provided by the adaptor 105 according to the sensed battery voltageVbat and the voltage drop VCE;

Step 425: The sensing circuit 1104 is arranged to sense the chargingcurrent Ichr and check whether the charging current Ichr reaches themaximum charging current Imax that has been configured. If the chargingcurrent Ichr reaches the maximum charging current Imax, the flowproceeds to Step 430, otherwise, the flow proceeds back to Step 420.

Step 430: The sensing circuit 1104 is arranged to sense and checkwhether the actual power dissipation of the conductive circuit element1101 exceed above the power dissipation threshold Pdmax or not by usinga temperature sensor to detect the operating temperature of conductivecircuit element 1101. If the detected temperature is lower than atemperature threshold, this may indicate that the actual powerdissipation of conductive circuit element 1101 does not exceed above thepower dissipation threshold Pdmax and the flow proceeds to Step 435;otherwise, the flow proceeds to Step 450;

Step 435: The controlling circuit 1105 of portable device 110sets/configures the adjusted output charging voltage Vchg provided bythe adaptor 105;

Step 440: The sensing circuit 1104 is arranged to sense the batteryvoltage Vbat, and the controlling circuit 1105 is arranged to estimatewhether the sensed battery voltage Vbat is changed or not. If the sensedbattery voltage Vbat is changed, the flow proceeds to Step 420;otherwise, the flow proceeds to Step 445.

Step 445: The controlling circuit 1105 controls and keeps the adaptor105 to output the output charging voltage Vchg that has beenset/configured in Step 435; and

Step 450: End.

In Step 405, the portable device 110 is arranged to communicate with theadaptor 105 via the specific communication interface such as USBcommunication interface.

In practice, the USB communication interface may be implemented by usinga USB cable, and the portable device 110 can send information orcommands to the adaptor 105 via data line (i.e. D+ or D−) and/or powersupply line (i.e. VBUS) of the USB cable so as to control/adjust theoutput characteristics of the adaptor 105. It should be noted that theabove-mentioned example is not meant to a limitation of the presentinvention. Other examples of using different communication interfaces orusing different communication protocols to control/adjust the outputcharacteristics of the adaptor 105 should fall within the scope of thepresent invention.

In Step 410, before controlling the output characteristics of theadaptor 105, the portable device 110 is arranged to check whether theadaptor 105 is a controllable adaptor capable of supporting thiscontrollable scheme. In this embodiment, the adaptor 105 is acontrollable adaptor, and the flow proceeds to Step 415 so that theportable device 110 begins to control the output characteristics of theadaptor 105. However, if another adaptor not supporting thiscontrollable scheme is connected to the portable device 110, the flowproceeds to Step 450 and the portable device 100 is not arranged tocontrol the output characteristics of this adaptor.

In Step 415, the controlling circuit 1105 is arranged to configure thecharging current Ichr as the maximum charging current Imax so as toachieve the purpose of fast charging. However, in other embodiments, thecontrolling circuit 1105 can configure the charging current Ichr as acurrent that is slightly smaller than the maximum charging current Imax,to achieve the purpose of fast charging. This modification can alsoreduce the whole charging time effectively.

The above-mentioned temperature sensor employed by the sensing circuit1104 may be implemented by using a negative temperature coefficient(NTC) thermistor or a positive temperature coefficient (PTC) thermistor.The modifications of implementation of the temperature sensor shouldfall within the scope of the present invention.

Additionally, the portable device 110 can inform the adaptor 105 of thecondition of the battery 1103, and control the adaptor 105 todynamically provide/supply different output characteristicscorresponding to different operation modes. According to a thirdembodiment of the present invention, the adaptor 105 comprises a normalmode and a green mode (or called sleep mode). Under the normal mode, thecontrolling circuit 1105 of portable device 110 controls the adaptor 105to provide normal output characteristics such as a normal output power.The normal output characteristics may include AC-to-DC switchingfrequency, AC-to-DC bias current, the precision of output voltage,voltage ripple, and/or the dynamic loading, etc. The controlling circuit1105 can control the sensing circuit 1104 to sense the condition of thebattery 1103 (i.e. the loading condition), and control the adaptor 105to decrease the output characteristics of the adaptor 105 if it has beennot required for the adaptor 105 to charge the battery 1103. In thissituation, the controlling circuit 1105 is arranged to control theadaptor 105 to exit from the normal mode and enter the green mode orsleep mode. That is, the portable device 110 can sense the loadingcondition and control the adaptor 105 exit from the normal mode andenter the green mode or sleep mode according to the sensing result. Inaddition, the controlling circuit 1105 can also control the adaptor 105to decrease the output characteristics and control the adaptor 105 toenter the green mode or sleep mode if the controlling circuit 1105estimates that the portable device 110 switches from a heavy loadingcondition to a light loading condition.

Additionally, in other embodiments, the adaptor 105 may be designed asan adaptor device operating under the green mode or sleep mode accordingto the default setting. Under the green mode or sleep mode, thecontrolling circuit 1105 of portable device 110 controls the adaptor 105to provide the decreased/reduced output characteristics such as a loweroutput power. The controlling circuit 1105 can check whether the adaptor105 is connected to portable device 110 to charge the battery 1103, andcan control the adaptor 105 to increase the output characteristics ofthe adaptor 105 and control the adaptor 105 to exit from the green modeor sleep mode to enter the normal mode if it is required for the adaptor105 to charge the battery 1103. That is, the portable device 110 cansense the loading condition and control the adaptor 105 exit from thegreen mode or sleep mode and enter the normal mode according to thesensing result. In addition, the controlling circuit 1105 can alsocontrol the adaptor 105 to increase the output characteristics of theadaptor 105 so as to control the adaptor 105 to enter the normal mode ifthe controlling circuit 1105 estimates that the portable device 110switches from a light loading condition to a heavy loading condition.

In addition, the portable device 110 as shown in FIG. 1 employs thelinear charger structure; however, this is not intended to be alimitation of the present invention. Other types of charger structurecan be also applied into the portable device 110. For example, theportable device 110 can also employ the switching mode chargerstructure. This also falls within the scope of the present invention.

According to the above-mentioned embodiments, the portable device 110can communicate with the controllable adaptor 105 via a variety ofcommunication interfaces and control output characteristics of thecontrollable adaptor 105, to achieve the purpose of fast charging, avoidthermal damage, enhance/improve the whole charging efficiency, and tosave more power.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

1. A portable device capable of controlling output characteristics of anadaptor which is used for charging a battery of the portable device,comprising: a sensing circuit, for sensing a condition of the battery;and a controlling circuit, coupled to the sensing circuit, forcontrolling the adaptor to adjust its output characteristics based onthe condition of the battery.
 2. The portable device of claim 1, whereinthe output characteristics comprises a charging current, a chargingvoltage, a switching frequency, a bias current, a precision of outputvoltage, a voltage ripple, and a dynamic loading.
 3. The portable deviceof claim 1, wherein the sensing circuit is arranged to sense a batteryvoltage of the battery, and the controlling circuit is arranged tocontrol the adaptor according to the sensed battery voltage.
 4. Theportable device of claim 3, wherein the controlling circuit is arrangedto configure a charging current and then to adjust a charging voltageaccording to the sensed battery voltage.
 5. The portable device of claim3, wherein the controlling circuit is arranged to configure a chargingcurrent as a maximum charging current which can be supplied by theadaptor based on the sensed battery voltage.
 6. The portable device ofclaim 5, wherein the controlling circuit is arranged to determine thecharging voltage provided by the adaptor according to the maximumcharging current and a power dissipation threshold, and to control theadaptor to output the determined output voltage and the maximum chargingcurrent.
 7. The portable device of claim 6, further comprising: aconductive circuit element, coupled between the battery and an input ofthe portable device; wherein the sensing circuit is arranged to sense avoltage drop across the conductive circuit element and the controllingcircuit is arranged to estimate the maximum charging current accordingto the power dissipation threshold and the voltage drop.
 8. The portabledevice of claim 3, wherein the charging current determined by thecontrolling circuit is inversely proportional to a voltage differencebetween the charging voltage and the sensed battery voltage.
 9. Theportable device of claim 3, wherein the controlling circuit is arrangedto configure a charging voltage and then to adjust a charging currentaccording to the sensed battery voltage.
 10. The portable device ofclaim 9, wherein the controlling circuit is arranged to configure thecharging voltage and then to adjust the charging current according tothe sensed battery voltage, to keep the adaptor supply/provide a ratedoutput power substantially.
 11. The portable device of claim 1, whereinthe sensing circuit is arranged to sense a loading of the battery, andthe controlling circuit is arranged to control the adaptor to decreasethe output characteristics of the adaptor and control the adaptor toenter a green mode or a sleep mode when the loading switches from aheavy loading condition to a light loading condition.
 12. The portabledevice of claim 1, wherein the sensing circuit is arranged to sense aloading of the battery, and the controlling circuit is arranged tocontrol the adaptor to raise up the output characteristics of theadaptor and control the adaptor to exit from a green mode or a sleepmode when the loading switches from a light loading condition to a heavyloading condition.
 13. A method for employing a portable device tocontrol output characteristics of an adaptor which is used for charginga battery of the portable device, comprising: sensing a condition of thebattery; and controlling the adaptor to adjust its outputcharacteristics based on the condition of the battery.
 14. The method ofclaim 13, wherein the output characteristics comprises a chargingcurrent, a charging voltage, a switching frequency, a bias current, aprecision of output voltage, a voltage ripple, and a dynamic loading.15. The method of claim 13, wherein the step of sensing the condition ofthe battery comprises: sensing a battery voltage of the battery; and thestep of controlling the adaptor to adjust its output characteristicsbased on the condition of the battery comprises: controlling the adaptoraccording to the sensed battery voltage.
 16. The method of claim 15,wherein the step of controlling the adaptor according to the sensedbattery voltage comprises: configuring a charging current; and adjustinga charging voltage according to the sensed battery voltage.
 17. Themethod of claim 15, wherein the step of controlling the adaptoraccording to the sensed battery voltage comprises: configuring acharging current as a maximum charging current which can be supplied bythe adaptor based on the sensed battery voltage.
 18. The method of claim17, wherein the step of controlling the adaptor according to the sensedbattery voltage further comprises: determining the charging voltageprovided by the adaptor according to the maximum charging current and apower dissipation threshold; and controlling the adaptor to output thedetermined output voltage and the maximum charging current.
 19. Themethod of claim 18, further comprising: sensing a voltage drop across aconductive circuit element coupled between the battery and an input ofthe portable device; and estimating the maximum charging currentaccording to the power dissipation threshold and the voltage drop. 20.The method of claim 15, wherein the charging current is inverselyproportional to a voltage difference between the charging voltage andthe sensed battery voltage.
 21. The method of claim 15, wherein the stepof controlling the adaptor according to the sensed battery voltagecomprises: configuring a charging voltage; and adjusting a chargingcurrent according to the sensed battery voltage.
 22. The method of claim21, wherein the step of controlling the adaptor according to the sensedbattery voltage further comprises: keeping the adaptor supply/provide arated output power substantially.
 23. The method of claim 13, whereinthe step of sensing the condition of the battery comprises: sensing aloading of the battery; and the method further comprises: controllingthe adaptor to decrease the output characteristics of the adaptor andcontrolling the adaptor to enter a green mode or a sleep mode when theloading switches from a heavy loading condition to a light loadingcondition.
 24. The method of claim 13, wherein the step of sensing thecondition of the battery comprises: sensing a loading of the battery;and the method further comprises: controlling the adaptor to raise upthe output characteristics of the adaptor and controlling the adaptor toexit from a green mode or a sleep mode when the loading switches from alight loading condition to a heavy loading condition.
 25. An adaptorused for charging a battery of a portable device, wherein an outputcharacteristic of the adaptor is configurable according to a conditionof the battery.